Host processor systems may store and retrieve data using a storage device containing a plurality of host interface units (host adapters), disk drives, and disk interface units (disk adapters). Such storage devices are provided, for example, by EMC Corporation of Hopkinton, Mass., and disclosed in U.S. Pat. No. 5,206,939 to Yanai et al., U.S. Pat. No. 5,778,394 to Galtzur et al., U.S. Pat. No. 5,845,147 to Vishlitzky et al., and U.S. Pat. No. 5,857,208 to Ofek. The host systems access the storage device through a plurality of channels provided therewith. Host systems provide data and access control information through the channels of the storage device and the storage device provides data to the host systems also through the channels. The host systems do not address the disk drives of the storage device directly, but rather, access what appears to the host systems as a plurality of logical volumes. The logical volumes may or may not correspond to the actual disk drives.
In-place data modification involves the translation, transformation and/or other modification of data on a storage device while that data is being actively accessed by one or more applications. In-place data modification techniques may include in-place encryption (or re-encryption) of data. A known approach for in-place data modification is the disruptive unloading of data to be modified and the reloading of the newly formatted or encrypted data. However, the disruptive unload/reload approach has the disadvantage that applications cannot access the data during the unload/reload process. Another approach involves the non-disruptive migration of data to a new device, such as by using Logical Data Migration Facility (LDMF). However, a non-disruptive migration tool may require increased permanent space requirements and data is not backed-up while the data is being transformed.
Accordingly, it would be desirable to provide a system that facilitates non-disruptive access of an application to data undergoing in-place data modification on a source device without needing extra permanent migration space and with less risk of data loss.